Generally, the prior art uses two separate and non-releated forms for delivering drugs, mainly the tablet and the osmotic device. The tablet is a solid dosage form, which may be molded or compressed, and contains a drug that is delivered by the tablet dissolving or disintegrating in a short time. A tablet made with a hole for releasing drug also is known to the prior art. For this tablet, the hole is made in a step that is the end step for manufacturing the tablet. For example, in U.S. Pat. No. 3,146,169 issued to Stephenson et al there is disclosed a tablet made by compressing an inert material around a medicated material with a hole punched through the outer, inert material. The hole extends into the medicated portion, and after the tablet is swallowed the medicament is released into the gastrointestinal tract by gastric fluid leaching it through the hole. The nature and rate of drug release for this tablet is determined by fluid leaching in an out of the hole as governed by the environment.
Osmotic devices for dispensing drugs are totally unlike the above described tablets. Osmotic devices are so named by the art because they dispense drug by physical and chemical principles comprehensive and fundamental to an osmotic device. Also, they are labelled as devices because the osmotic device governs the release pattern of the drug independent of the environment, and because they maintain their integrity during the dispensing period. In U.S. Pat. Nos. 3,845,770 and 3,916,899 issued to Theeuwes et al, there is disclosed an osmotic device comprising a semipermeable wall surrounding a compartment containing drug with an outlet passageway through the wall. The passageway, or hole, in osmotic devices, (a hole through the wall is by convention referred to as a passageway), is mechanically or laser drilled through the wall as the final manufacturing step, after the wall is formed on the device. Drug is released by fluid being imbibed through the wall, as the result of an osmotic pressure gradient across the wall, forming a solution containing drug in the compartment, which solution is osmotically pumped through the outlet passageway from the device over time.
While the above-described osmotic device represents a true advancement in the drug delivery art, it will be appreciated that if a process is made available for manufacturing an outlet passageway as an inherent part of the manufacture of the device, such a process would be a useful contribution to the art. Likewise, it will be appreciated by those versed in the art, that if a process is provided that eliminates a manufacturing step, or combines manufacturing steps into lesser or a single step, such a process also would be a valuable and practical contribution to the art.